(1) Field of the Invention
The present invention relates to devices or systems for entering information into a data processing machine. More specifically, the present invention relates to devices and systems that capture and store information related to hand written or hand drawn text, characters, symbols or graphics.
(2) Description of Related Art
A computer system typically includes an alphanumeric keyboard that enables users to enter commands and data in a text format to be processed by a data processing machine such as a computer. Keyboards are the most commonly used input devices for computers. However, keyboards require users to develop skills in typing, they are not well suited for entering graphics data, and they are usually tethered to the computer by means of a cable. Additionally, keyboards require users to learn many particular keystroke sequences to invoke corresponding computer commands, requiring more time to implement and more effort to learn.
A variety of additional input devices have been proposed and implemented for use in connection with computers, to work as adjuncts to the common keyboard, or as an alternative for applications for which the keyboard is not well suited. One input device commonly used is the mouse pointing device that is efficient for invoking particular computer commands. This device is typically connected to the computer by way of an electrical cable and must be used in close proximity to the computer. The mouse pointing device functions satisfactorily for the purpose of initiating particular computer functions, but users regard the device as awkward and imprecise for entering text and graphics data.
Other input devices include digitizer tablets that involve the use of a flat touch pad which can be touched by a stylus. The pad senses the location of the touching object usually by resistance or capacitance disturbances in a field associated with the pad. Digitizer tablets perform well for entering graphics, report absolute position well, but are impractical for entering textual data.
Certain tablets have been proposed by which both graphics and textual data could be entered in a computer using a stylus. These devices are typically tethered to the user's computer by an electrical cable, and provide no memory storage to permit autonomous usage. Further, these devices are inconvenient for the user due to their physical dimensions. Most users, would find it desirable to have a computer input device that: is autonomous, i.e. untethered by cable connection to a computer; permits easy and precisely controllable input of both text and graphics data; fits in the hand like a pen or pencil for ease of use; affords memory capacity to store accumulated input of data of most users over the course of a day; and can be carried unobtrusively in a user's pocket.
Furthermore, recently there has been an increased interest in input devices or systems that may be used for manually entering data in the computer and also for handwriting recognition and signature verification. These devices utilize a pen or stylus for tracing a path on a resistive grid or capacitive grid on a graphics tablet or computer screen. The computer digitizes the information conveyed by the pen when the pen crosses a certain predetermined point on the grid. Data processing is then utilized for processing a two-dimensional pattern produced on the grid to determine the motion of the pen. Data processing further processes the information as an image information.
However, these devices do not produce an accurate recording of the text or graphics that have been input via the tablet or the screen. Considerable information indicative of the motion of the pen is lost in the processing of data. One reason is that data describing the motion of the pen is undersampled. The sampling of the pen tip position is performed first spatially as the tip of the pen crosses the resistive or capacitative elements which make up the grid. The pen tip position is also sampled temporarily by the electronics which scan the grid. For such grid devices, a finer resolution may be required to provide sufficient data for handwriting recognition. However, when finer resolution is provided, grid cost dramatically increases. Another disadvantage of these devices is that processing is performed essentially as a two-dimensional or spatial pattern recognition and the amount of processing for handwriting recognition increases nearly as the square of the number of samples. Moreover, when a pen input device is utilized for handwriting or graphics, an additional dimension, such as a third dimension and rotation about each axis in connection with the three dimensions, involved in the motion of the pen input device, must be measured to provide accurate information about two-dimensional tracing on a writing surface in connection with text or graphics input to the computer. This additional information may, for example, provide information about the Z coordinate or the rotation of a predetermined point of the pen input device in the course of its motion.
To eliminate the difficulty posed by rotation, some conventional input devices have focused on detecting the motion of the pen in two dimensions. In these devices, the elements measuring the motion of the pen in two dimensions are placed intermediately pen input device relative to an axis passing through a tip of the pen and free end of the pen located away from the tip. Also, these elements may be placed at the free end of the pen input device. However, the measurement in two directions (X and Y) recorded by these elements is not accurate as the farther these elements are from the tip of the pen, the more a measurement in the third dimension (Z axis) and measurement of the rotation about each axis is necessary to accurately reflect the motion.
It is desirable to provide an input device that provides an accurate detection of the two dimensional motion of the tip of the pen on the writing surface thereby providing accurate information about the text or graphics input to a computer. The rotation of the input device about the tip of the pen and around the axes of the pen particularly poses significant problems in its measurement and "interpretation" thereof with respect to the text or graphics information input to the computer. Furthermore, it is desirable to provide an input device that eliminates the difficulty connected to accurate measurement of rotation explained above. Moreover, it is desirable to provide an input device at a lower cost than the cost of a grid with fine resolution. Also, it is desirable to provide an input device such as a marking device that can use existing paper/tablet as writing surface so that the user of the pen may also see the mark the marking device leaves on the writing surface as the marking device is utilized for text or graphics. It is also desirable to provide a marking device that captures and stores detailed information about the dynamic motion of the marking device as it is used in writing, drawing, and illustration.